Currently, certain substances having a low specific gravity and a low vapor pressure are stored in underground, i.e. subterranean caverns, in liquid form. Exemplary substances are liquid natural gas (LNG), isobutane and propane. Liquid natural gas, for example, may be maintained in a liquid state at approximately 60.degree. F. under a pressure of approximately 30 psi. Thus, placing such substances in large, subterranean caverns provides a way to maintain large quantities of the substance in liquid form during storage.
An exemplary subterranean, storage cavern may be formed by washing away the salt from a natural salt mine to create a cavern. The substance, such as liquid natural gas, is then pumped into the storage cavern and stored in this cool environment under sufficient pressure to maintain the substance in liquid form. A current method for producing the liquid from the storage cavern is to use brine to force the product from the cavern. This technique requires a separate pond, typically at the earth's surface, for storage of the brine when the cavern is full of the desired substance. A pump is utilized in moving the brine from the pond and into the cavern to force the liquid product from the cavern. The surface brine ponds are extremely expensive to build and maintain.
It would be advantageous to eliminate the use of brine introduced into the storage cavern for moving the low specific gravity liquid to a location at or above the surface of the earth.